Flow Pattern Transition During Gas Liquid Upflow Through Vertical Concentric Annuli—Part II: Mechanistic Models

Abstract

In this paper the transition boundaries between different flow regimes during cocurrent upflow of gas liquid two-phase mixture through concentric annuli has been predicted theoretically. On the basis of the experimental observations (Das et al., 1999), mechanistic models have been proposed to formulate mathematical equations of the regime boundaries as functions of the annulus dimensions, the physical properties, and velocities of the two phases. The analysis has yielded the bubbly-slug transition to occur at a limiting void fraction of 0.2, and the slug-churn transition to occur due to flooding of the liquid films by the Taylor bubbles. A comparison of the model predictions with experimental data corroborate the suitability of the proposed mechanisms.